(1) Applications of the Invention
This invention relates to a method of manufacturing glass as a material for optical transmission fiber.
(2) Description of the conventional method
The method of manufacturing glass rods of this kind has been known as Bernouilli's Method. In this method, a hydride, halide or oganic compound of Si or other elements are mixed with a gas capable of oxidizing, such as O.sub.2. This mixture is fed into the flame of a high frequency plasma torch or oxy-hydrogen burner. When the mixture is heated in the flame, the glass formation takes place. Then, this glass is piled up on the top of a rotating glass rod of SiO.sub.2 and other oxides, and a glass rod is thus manufactured.
Processes for making an optical fiber waveguide are briefly described in the following. The shape of the rod is to be determined in accordance with the application of the optical fiber. A rod with uniform distribution of refractive index is inserted into the hollow of the tube which has uniform distribution of refractive index. This composite is heated at the temperature high enough to fuse the composite material. Then the fusing composite is drawn to produce a fine solid fiber for optical waveguides comprising a core with a surrounding clad.
In this method, the manufacturing processes are complicated. The transmission loss of the fibers manufactured in this method is not low enough to satisfy requirements for modern optical communications because undesirable contaminations would be introduced between the rod and the pipe. The defects of the interface between the rod and the tube cause the transmitting light to scatter or to be absorbed mainly by the material located in the interface.
In addition to the disadvantages mentioned above, a fiber having a desired distribution of refractive index in the radial direction cannot be obtained because it is made from a combination of the rod and the tube with uniform refractive index. Furthermore the manufacturing processes are complicated and the final products are expensive compared to those made by the present method. For this reason, the conventional method is not suitable for mass-production.